The effects of environment and lifestyle on eye growth

Abstract

Aims: To investigate the association between subjectively and objectively measured environmental and lifestyle factors on eye growth. Rationale: Emmetropisation is the process of visual regulation of eye growth towards an optimal refraction. Disruptions in emmetropisation have been thought to lead to the development of myopia which has increased in prevalence worldwide. It is a condition which brings significant socio-economic burden and sight-threatening complications. This has led to a significant interest in furthering our understanding of the influential factors driving eye growth, which is the focus of this thesis. Methods: Two age cohorts were recruited, 226 aged 7 – 12 years and 87 aged 18 – 25 years. 55.3% (n=173) were followed up longitudinally after 12 months and 18.5% (n=58) after 24 months. Time spent outdoors was measured by both subjective and objective methods, including questionnaires, a wrist-worn actigraphy device and a surrogate biomarker, Conjunctival UV autofluorescence (CUVAF). Other lifestyle factors were assessed via questionnaires. Results: Significant differences in objectively measured light exposure were found between seasons and day of the week. UK children were found to spend more time outdoors on weekdays than weekends. This study has shown for the first time a lack of CUVAF in UK children and a low prevalence of CUVAF in UK young adults. This suggests that CUVAF may not be a suitable surrogate measure of time outdoors in the UK. A normative dataset of sleep patterns of UK children is presented and has shown emerging evidence that sleep/wake cycles are altered in myopes. Urbanisation, BMI and birth weight were found to be significantly associated with eye growth, however all other factors were found not be to significant. Conclusions: The role of illuminance and eye growth is a prominent area of current research and this study has provided valuable data on environmental risk factors in the UK.